Over the last few years, we saw numerous new battery technologies being proposed by different research institutes. There was news of flexible Li-ion batteries and even batteries made from graphene. However, no one is really sure how long it would take to get these new technologies into commercial form and therefore there is no point in waiting for them at this point of time.
If you cannot increase the amount of charge available for your device, the next best thing is to increase the amount of work that it can do with the same amount of charge. That is why we decided to check with the top engineers in the industry how they have been enhancing battery life in their devices.
How to save power
There are umpteen areas that you can focus on to save power in a system. The major ones are discussed below.
Select the right component. While working on a project that focuses on operating with very low power consumption, it is of paramount importance to choose components that improve the power system performance within the constraints of the project’s current budget. One way to do this is to utilise power saving techniques on top of your low-power components.
Brian Chu, senior application engineer, Microchip Technology, says, “In addition to selecting low-supply-current devices, it is recommended that designers take advantage of various power-saving techniques such as load-based multi-mode power-conversion design, input-to-output bypass design, standby and the like while maintaining the performance level.”
Fortunately, all the latest components available play a part in helping engineers design more efficient circuits. The latest power switches offer very low resistance, standby and shutdown current, and also protect against current-overload and short-circuit conditions in a circuit. On the other hand, the latest low-dropout regulators (LDOs) make less noise and offer high ripple rejection and low standby current.
“Moreover, current microprocessor supervisory circuits offer voltage-monitoring, power-up reset and watchdog functions. A combination of these solutions will enable engineers to build more efficient circuits that would consume much less power. For embedded designs, engineers can utilise microprocessor supervisory circuits, power switches and LDOs,” explains Kay Annamalai, director of marketing, Pericom Semiconductor.
Another important aspect is the quiescent current of the components being used in the system. Quiescent current is the current flowing through the system or component when no load is being driven.
Abhishek Kumar, business development manager-power management, Texas Instruments (India), shares, “Quiescent current is important because battery life is determined by the total current drain composed of quiescent current (mainly in standby conditions) and load current. Quiescent current consumption should be as low as possible in order to prolong the battery’s life.”
Improve your power system performance. Faster, lower-loss switching topologies such as zero current switching, zero voltage switching and sine-amplitude conversion are allowing significant improvements in power system performance.
“Reductions in the overall size of power components and increases in conversion efficiency are opening up opportunities for integrating power management solutions adjacent to their demanding loads, microcontrollers and FPGAs, right on the main PCB,” informs Andy Gales, vice-president, international sales, Vicor Corporation.
Tuning the code
Mobile devices typically have their operating systems tuned for better battery life by making several special features available to designers. Android utilises a system called ‘wakelocks,’ which is a set of patches to the Linux kernel that allow a caller to prevent the system from going to low-power state.
“If a novice programmer created a buggy code where it would acquire wakelock and then get into some loop somewhere, the device would hold wakelock and never go into standby mode,” explains Darshak Vasavada, CEO, Stamp Computers.
It is a myth that only hardware dissipates power, and software does not play any role. In all the embedded systems it is the software that controls the hardware and thus plays an important part in optimising the power of the system as a whole. Nitin Gupta, lead engineer, µEnergy Applications, CSR India explains where and how to optimise. “Optimise the memory accesses in the software, as more frequent are the access, more time is used up in switching high capacity bus system and also the memory system. You can also use parallel processing of the memory system to access more data in one access. Another tip is that all the IPs should be maintained in no-clock/lower-clock, if they are not required in the application so that the power dissipation is least, but it’s a trade-off with performance.”